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Move语义1: exercises/move_semantics/move_semantics1.rs
题目
rust
// move_semantics1.rs
//
// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand
// for a hint.
// I AM NOT DONE
fn main() {
let vec0 = Vec::new();
let vec1 = fill_vec(vec0);
println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
vec1.push(88);
println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
}
fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
let mut vec = vec;
vec.push(22);
vec.push(44);
vec.push(66);
vec
}题目解析
编译器提示信息如下：
txt
⚠️ Compiling of exercises/move_semantics/move_semantics1.rs failed! Please try again. Here's the output:
error[E0596]: cannot borrow `vec1` as mutable, as it is not declared as mutable
--> exercises/move_semantics/move_semantics1.rs:15:5
|
15 | vec1.push(88);
| ^^^^^^^^^^^^^ cannot borrow as mutable
|
help: consider changing this to be mutable
|
11 | let mut vec1 = fill_vec(vec0);
| +++
error: aborting due to previous error
For more information about this error, try `rustc --explain E0596`.从错误信息能读出的信息：
- 无法对不可变局部变量
vec1进行可变借用 - 提示我们添加在变量
vec1上添加mut
rust
fn main() {
let vec0 = Vec::new();
let vec1 = fill_vec(vec0);
let mut vec1 = fill_vec(vec0);
println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
vec1.push(88);
println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
}这个题目中，因为在调用fill_vec(vec0)函数的时候，将vec0当作参数传入，vec0由于是Vec类型，会Move转移所有权到fill_vec函数中。所以fill_vec(vec0)结束后，vec0应该是不可用的，你可以尝试再访问一下vec0试一下。